DE10234400B3 - Process for the production of hollow bodies from fiber-reinforced ceramic materials, hollow bodies and their use - Google Patents

Abstract

Process for the production of hollow bodies made of fiber-reinforced ceramic materials, whereby a green body is produced, containing compressible cores and a mass containing compressible binders and fibrous material, which is compressed with compression of the core, the green body is hardened and carbonized by heating in a non-oxidizing atmosphere and is pyrolyzed and optionally siliconized, hollow bodies produced in this way and their use in particular as a brake and clutch disc.

Description

The present invention relates refer to a process for the production of hollow bodies from fiber-reinforced ceramic Materials. In particular, the invention relates to a method for Near-net-shape production of a porous fiber-reinforced carbon molding with recesses or cavities, especially a fiber-reinforced one C / C body (carbon fiber reinforced carbon, English "CFC" or "CFRC", carbon fiber reinforced carbon), the binder-containing pulp by means of a pressing process using press cores molded and C / C in a subsequent thermal treatment is implemented, and if necessary the recompression of this porous fiber reinforced Carbon-containing molded body with the formation of a ceramic matrix, in particular by a Liquid metal infiltration in the C / C body, if necessary with subsequent Heat treatment the matrix then metals and those by reaction with the carbon formed metal carbides and optionally residues of unreacted Contains carbon.

"Metals" here means all elements form the carbides that are solid at room temperature, so too especially silicon.

The method according to the invention relates in particular the. Manufacture of ceramic composite materials reinforced with carbon fibers Recesses and cavities, which about the Liquid metal infiltration with silicon melts reacting at least part of the carbon to silicon carbide in composite materials reinforced with carbon fibers SiC-containing or carbon and SiC-containing matrix (C / SiC or C / C-SiC materials) be implemented. These composite materials are used in particular for brake, clutch and friction discs, as well as high temperature resistant construction materials.

Mainly used materials nowadays for brake discs in automotive engineering are steel or cast iron, and in aviation with Reinforced carbon fibers Carbon Materials (C / C). The properties required by the lens materials are high mechanical stability, temperature resistance, Hardness and wear resistance across from the friction partner in the friction pairing of the brake. The operating temperature previously used cast iron brake discs is limited by the melting point of the material. The mechanical Failure temperature is dependent from the load, already well below the melting point. Furthermore, due to transformation of the metallic structure Heating the risk of cracking in the slices. The use of fiber reinforced ceramics as material for Brake disc applications have proven to be a solution to this problem. In particular Materials based on silicon carbide reinforced with carbon fibers (C / SiC) have opted for this application proved to be suitable. The advantages of this material are the lower density (thus lower weight with the same Volume), the high hardness and temperature resistance up to approx. 1400 ° C and last but not least the extremely high wear resistance. That much less The weight of brake discs made from these C / SiC materials has been proven as a positive influencing factor to improve comfort and safety through the reduction of unsprung masses in motor vehicles and as more economical Factor in the field of aviation. The great hardness and wear resistance of C / SiC components enables here far higher Tool life compared to the usual C / C-based materials or metal base.

• – Herstellen einer preßfähigen Mischung aus Kohlenstoff-haltigen Fasern oder Faserbündeln (gemeinsam nachfolgend als "Faserstoff" bezeichnet), die mit einer Beschichtung überzogen sein können, einerseits und Füllmitteln und/oder Bindemitteln wie beispielsweise Harzen und/oder Pech andererseits,
• – Formgebung der Mischung unter Druck und Temperatur und Carbonisierung der Kohlenstoff-haltigen Füll- und Bindemittel zur Herstelluug eines Formkörpers, insbesondere eines aus mit Kohlenstoffasern verstärktem Kohlenstoff bestehenden Formkörpers (C/C) und gegebenenfalls Graphitierung
• – Infiltrieren zumindest einer Randschicht des Formkörpers mit einer Silicium-Schmelze und zumindest partielle Reaktion des Siliciums mit dem Kohlenstoff im Formkörper zu SiC, wobei sich ein Formkörper bildet, der wenigstens in der Randschicht aus einer Verbundkeramik mit in einer Matrix aus überwiegend SiC, Si und C eingebetteten, Kohlenstoff-haltigen Fasern besteht (hier ebenfalls als C/SiC bezeichnet).

Methods for producing C / SiC components are, for example, from the DE 197 10 105 A1 known and include the following steps

• Producing a compressible mixture of carbon-containing fibers or fiber bundles (collectively hereinafter referred to as "fibrous material"), which can be coated with a coating, on the one hand, and fillers and / or binders such as, for example, resins and / or pitch,
• - Shaping of the mixture under pressure and temperature and carbonization of the carbon-containing fillers and binders for the production of a shaped body, in particular a shaped body (C / C) consisting of carbon fiber reinforced carbon and optionally graphitization
• - Infiltrating at least one edge layer of the shaped body with a silicon melt and at least partial reaction of the silicon with the carbon in the shaped body to form SiC, a shaped body being formed which consists at least in the outer layer of a composite ceramic with a matrix of predominantly SiC, Si and C embedded, carbon-containing fibers (also referred to here as C / SiC).

The following is general under C / SiC also the material variant can be understood, in which, as described above only one edge layer is siliconized.

The usual manufacturing processes also include those in which the C / C body is in the liquid or gas phase with carbon precursors ("carbon precursors", substances which form carbon when heated with the exclusion of oxidizing media) or with carbon is post-compressed, or the matrix of predominantly SiC, Si and C by gas phase infiltration (CVD, Chemical Vapor Deposition, or CVI, Chemical Vapor Infiltration) or by the pyrolysis of Si-containing preceramic polymers is generated.

Today's metallic brake discs often own air flowed through Ventilation slots or -channels inside the disc to reduce the temperature level of the disc and the wear of the friction linings lower at high load. Such ventilation ducts are also used for brake discs based on C / SiC, especially around the temperature level consideration on the brake pads and lower other system components.

A method for producing friction units made of C / C-SiC material with ventilation channels, cavities and recesses, in which a porous carbon body structured close to the final contour is infiltrated with liquid silicon, is known from US Pat EP 0 788 468 B1 known. This method takes advantage of the fact that the silicon liquid infiltration and formation of the Si and SiC-rich composite matrix takes place almost without changing the geometry of the C / C preform, so that the cavities and recesses are already in the relatively soft and easy-to-process C / C - Pre-body can be created and not only in the very hard C / C-SiC composite ceramic. Among other things, it is proposed to form the cavities and recesses by soluble cores made of foam polystyrene or other rigid foams, by pyrolyzable cores made of polyvinyl alcohol, or by removable cores made of rubber, metal or ceramic. The material of the cores depicts the ventilation ducts of the friction unit, the webs between the individual ventilation ducts being predetermined by corresponding cutouts in the core material.

From the older application according to DE 101 48 659 A1 a method is known for producing hollow bodies from fiber-reinforced ceramic materials. Cores are used in a compressible mass containing fibers made of carbon and thermally curable binders. The cores are made of a material that is not meltable and at least shrink above the hardening temperature of the compression molding of the pressable class. 10% of their original volume.

The in the production of short fiber reinforced ceramics Fibrous molding compounds used can generally only fill the mold as a relatively loose pile. Therefore, for the manufacture from Grünlingen suitable bulk density, high compression ratios of pressable pale or high travel distances of the press rams necessary. In the discoid Zone within the molding compound, in which the cores are located (hereinafter referred to as "core zone") or in the Recesses between the cores, the molding compound can only imperfect these recesses to fill, since the molding compound prevented from flowing by the cores delimiting the recesses becomes. Therefore, the compression ratio in the core zone, namely in the gaps and gaps between neighboring cores always less than in the above and layers of material lying under the core zone. The fiber content in these areas the lower compression means less than in the rest of the material. This can be particularly harmful Influence on exert the mechanical properties of the fiber-reinforced ceramic.

Here, fibers are called short fibers with a medium length of at most Designated 50 mm.

This can be remedied among other things be created that the molding compound in the recesses between the cores using suitable press rams is pre-compressed. However, this procedure has some disadvantages on. So it is procedurally complex, because among other things to the normal pressing process the additional Filling process steps the core gaps with the molding compound and add their pre-compression. Suitable pressing tools would have to be stamped in several levels, of which those in the area of Recesses of the cores opposite the rest of the press tool can be moved separately. Furthermore, there can be a boundary layer or material and structure phase boundary between the pre-compressed areas in the core zone on the one hand and the one above or form underlying layers on the other hand. This is particularly so for the mechanical properties of the ceramic composite material obtainable thereby harmful.

The object of the invention is therefore to provide a method and an adapted core material to develop through which fiber-reinforced ceramic hollow bodies can be obtained, which in the core zone (more precisely in the recesses filled with molding compound between the cores) have no lower fiber density than in the about that or underlying layers, and the no phase boundary at the transition between the material of the core zone and the material of the above or below Have layers. The cores should continue to be such that they can be gently removed from the hollow body in a simple manner.

The object is achieved in that for a pressing process with the whole area of the compact capturing ram compressible cores are provided, at least in the direction the travel of the ram during the pressing process a change in length of experience at least 5%, with the cores made of one material, either in the further thermal treatment of the fibrous preform Completely be pyrolyzed, or at least partially with volume shrinkage be decomposed.

• – im ersten Schritt kompressible Kerne hergestellt werden, deren Form zumindest in der Ebene senkrecht zur Preßrichtung im wesentlichen der Geometrie der zu bildenden Hohlräume entspricht,
• – im zweiten Schritt ein Grünkörper hergestellt wird, indem in eine Form die genannten kompressiblen Kerne und eine preßfähige Bindemittel und Faserstoff enthaltende Masse gefüllt werden,
• – im dritten Schritt die faserstoffhaltige Masse verpreßt wird, wobei der Kern zumindest in Preßrichtung um mindestens 5 % seiner Ausdehnung in Preßrichtung komprimiert wird,
• – im vierten Schritt die faserstoffhaltige Masse ausgehärtet wird, bevorzugt durch Erwärmen auf eine Temperatur von 120 °C bis 280 °C, wobei der dritte und vierte Schritt auch gleichzeitig oder zeitlich teilweise überlappend ausgeführt werden können,
• – im fünften Schritt der auch als Vorkörper bezeichnete verfestigte Grünkörper durch Erhitzen in einer nicht oxydierenden Atmosphäre auf eine Temperatur von ca. 750 °C bis ca. 1100 °C zu einem C/C-Körper carbonisiert wird, und gegebenenfalls
• – im sechsten Schritt der C/C-Körper unter Erhalt seiner Form mit einem flüssigen Metall infiltriert wird, wobei zumindest teilweise eine Reaktion des Kohlenstoff-Anteils der Matrix des C/C-Körpers mit dem Metall unter Bildung von Carbiden abläuft,

wobei die Kompressibilität der Kerne unter den Preßbedingungen eine Längenänderung in Preßrichtung um mindestens 5 % zuläßt, und die Kerne aus Material bestehen, das im fünften Schritt pyrolysiert, oder unter Volumenschwindung zumindest teilweise pyrolysiert wird.The invention therefore relates to a method for producing hollow bodies from fiber-reinforced ceramic materials, wherein

• Compressible cores are produced in the first step, the shape of which essentially corresponds at least in the plane perpendicular to the pressing direction to the geometry of the cavities to be formed,
• In the second step, a green body is produced by filling the compressible cores mentioned and a mass containing pressable binder and fibrous material into a mold,
• In the third step, the pulp-containing mass is pressed, the core being compressed at least in the pressing direction by at least 5% of its extent in the pressing direction,
• In the fourth step, the fibrous mass is cured, preferably by heating to a temperature of 120 ° C. to 280 ° C., the third and fourth steps also being able to be carried out simultaneously or partially overlapping in time,
• - In the fifth step, the solidified green body, also referred to as the preform, is carbonized to a C / C body by heating in a non-oxidizing atmosphere to a temperature of about 750 ° C. to about 1100 ° C., and if appropriate
• In the sixth step the C / C body is infiltrated with a liquid metal while maintaining its shape, at least partially a reaction of the carbon portion of the matrix of the C / C body with the metal takes place to form carbides,

wherein the compressibility of the cores under the pressing conditions allows a change in length in the pressing direction by at least 5%, and the cores consist of material which is pyrolyzed in the fifth step, or at least partially pyrolyzed with volume shrinkage.

A mass is referred to as "pressable" if after compression in the pressing process keeps its shape when relaxing and not easily crumbled.

The fiber-reinforced ceramic produced according to this process hollow body are characterized by the fact that they a fiber density within the material in the area of the core zone have no less than that in the layers above and below is that the Material is homogeneous and no phase boundaries at the transition between the core zone and the adjacent material layers are recognizable.

According to the invention this is achieved in that Process compressible cores are used during the pressing process at least in the pressing direction pressed together or compressed. The change in length can be specifically adjusted by the material and type of the lost core. Across from A process with rigid cores results in a larger mold filling volume to disposal posed. While of the pressing process the compressible core is brought together to a predetermined length, as a result, the compression ratio of the pressable mass is in the recesses between the cores adjustable.

Preferred cores are: yourself during of the pressing by at least 5% based on their initial length or have it compressed. The spring force the material is preferably so low that the cured green body when Relaxation not harmed can be. For this reason, for example, elastomers or Rubber is not suitable as the core material.

The linear compressibility of the cores according to the invention, thus the relative change in length in the direction of the travel of the ram is at least 5% of the initial length. The cores are preferably from 2 to 80% and particularly preferred to 5 to 25% of their original length in the pressing direction compressed.

The strength of the cores chosen so the existence pressing pressure in the range of 0.1 to 50 MPa to achieve the desired Compression or compression is sufficient.

In general, such core materials preferably used, the melting temperature = is above the curing temperature of the green body.

According to one embodiment of the invention, the cores are produced from meltable materials, which are selected from thermoplastic and residue-free pyrolyzable polymers (plastics), hereinafter also called thermoplastic cores. According to the invention, the thermoplastic material for the core is selected so that its melting point is above the curing temperature of the shaping process for the green body, typically in the range from 120 to 300 ° C., but clearly below the carbonization temperature of the pressed and hardened green bodies. The melting point is usually at least 150 ° C., preferably at least 180 ° C. and particularly preferably between 220 ° C. and 280 ° C. However, if the pressable mixture is thermally cured only after the press has been brought together to the final dimension, then such core materials can also be used which melt or decompose at or below the curing temperature, since the pressable mass has then already assumed its final contour. If phenolic resins are chosen as binders for the pressable mixtures, the melting point of the thermoplastic is preferably above 150 ° C., for example. For the preferred compression molding and hot curing of the binders, high demands are placed on the thermoplastic core in terms of heat resistance. The heat distortion temperature (determined according to ISO 75 A ) is usually above 80 ° C, particularly preferably at least 150 ° C. The hardness (ball indentation hardness) of the thermoplastic should be at least 30 MPa.

Are used as material for the cores Thermoplastic materials used, so the production takes place the cores preferred over an injection molding process. In general, the known molding processes, such as cold or hot pressing, Casting, die casting or machining Processing, depending on the material used.

Advantageous materials for compressible press cores are foamed Polymers. Thermoplastic polymers are preferred, in particular those which can be pyrolyzed without residue. Particularly suitable polymers are polyamides (PA) such as PA 66, polyimides (PI) like polyetherimide (PEI) or modified polymethacrylimide (PMI), polyoxymethylene (POM) and polyterephthalates (PETP, PBTP) and their copolymers. Particularly suitable polymer foams are PMI foam and foamed Polystyrene.

In addition to the residue-free at temperatures of at least 750 ° C pyrolizing polymers are also suitable for those who only be partially pyrolyzed or carbonized, provided this is an essential one (at least 50%) volume shrinkage takes place. About these polymers belong including thermosets, such as phenolic resins or from these formed rigid foams. It is also possible, Mixtures of materials for to use the cores, some of which pyrolyze without residue, and another part in pyrolysis loses its original shape so far, that he is in the form of a loose powder or disjointed grains.

However, it is also possible to use a to use loosely bound pile of polymer balls.

In a further advantageous variant The invention relates to multi-layer cores made of foamed polymers used in sandwich-like structures. It is provided that at least one of the top or bottom surfaces of the core through a hard, infusible under hardening conditions, in particular a carbonizable polymer is covered. Especially both the upper and the lower surface of the core is preferred by such Layer covered. This ensures that the molding compound is not large in direct contact with the relatively soft compressible material made of polymer foam and not due to irregularities the undensified molding compound an uneven pressing of the core material. This should have been a wavy, rough and uneven surface of what was created here later Cavity. Due to the firmer material on the surfaces of the soft core, the pressing pressure is even in the compressible area of the core, so that smooth and flat interfaces are formed in the green body. The material that covers the soft cores is preferred for Temperatures of at least 750 ° C at least partially decomposed while decreasing in volume.

In a further variant, this will be hard material with the "sandwich construction" on the upper and / or lower bounding area the core is formed by a wood-based material; for example compressed wood or chipboard.

Another advantageous variant provides multi-part cores, the individual parts of which are under pressure are movable against each other. In such an embodiment the core consists of two half-cores or half-shells, one of which the first recesses in the inner area, which contains the second half core be able to record. The two half cores are initially by gluing or by a clip connection = held together can so in the mold be introduced. Only after the pressure has been applied does the adhesive or the clip connection tear, whereby the second half core can be pushed into the first. The first core is the leadership of the second. The travel path of the second core can by projections in the recess of the first Kernes or precisely set by the depth of the recess itself become.

The inventive method provides that in the second Crushable masses made of carbon fibers, thermally curable binders, and - in particular Carbon-containing aggregates together filled with the cores described above in the mold. The Geometry of the formed body established.

The carbon fiber layers are preferred of the C / C pre-body nearby of the core in the given preferred direction of the carbon reinforcing fibers built on the core. Therefor such pressable masses are preferred used the carbon fibers with an average length of contain at least 5 mm. Pressable compositions are particularly preferred, the carbon fibers in the form of short fiber bundles with an average length of at the most 50 mm included, and with the fibers a coating of pyrolytic Have carbon made by carbonizing polymers, resins or pitch is formed. The compressible mass is then preferred so filled in the form that the Carbon fibers predominantly parallel to the direction of the highest Tensile stress of the resulting molded part are oriented. Mostly in this context means at least 50%. It is also possible that Cores with parallel and bound carbon threads (English "tapes" or "UDT" = unidirectional called tapes) and to wrap this envelope with thermal if necessary curable Fix binders. On this layer of preferred carbon fibers or threads then become common further pressable masses layered with shorter fiber or fiber bundle length.

In another preferred embodiment carbon fibers are used in the form of coated short fiber bundles. Graphitized carbon is particularly preferred Fibers, or fiber bundles with medium lengths below 5 mm.

As a thermally curable binder pitches such as coal tar pitch or petroleum pitch and / or preferably curable resins such as phenolic resins, epoxy resins, polyimides, filler-containing mixtures Furfuryl alcohol or furan resins are used. The masses become this in a mold filled, lost cores are provided in the form. Take the seeds the room the later cavities or recesses to be formed in the composite ceramic.

The third step is the shape after filling with the help of the ram pressurized with the required pressure and the mass becomes green bodies with cavities and / or pressed recesses.

In the fourth step, the pressed body is under Temperature hardened. curing can be done separately, i.e. after pressing, for example in an oven. It is also possible, hardening in a heatable press already during the Compressing simultaneously with this or with a delay kick off. When hardening in the form there are fewer requirements for holding the pressed, but still uncured body posed.

After hardening, the solidifies Green body in fifth Step together with the thermoplastic core in the C / C state, the is called carbonized. This is generally done by heating under Shielding gas (nitrogen) or in vacuum at temperatures in the range of approx. 750 ° C up to 1100 ° C. Becomes heated to temperatures above approx. 1800 ° C, there is also one Graphitization of the carbon instead.

After carbonizing the green body any pyrolysis or carbon residues in the cavities formed eliminated and it becomes a porous C / C body with cavities or receive recesses that can be recycled. He can reworked or assembled again to more complex structures or be glued.

In a preferred embodiment of the method according to the invention becomes the carbon of the C / C body in the sixth step by melt infiltration with metals and the subsequent one, if applicable heat treatment at least partially converted to the corresponding carbides. Prefers is the melt infiltration with silicon, whereby at least one Part of the carbon (preferably the carbon in the matrix) converts to silicon carbide; the matrix then contains SiC, unreacted Carbon and unreacted silicon. For this, the C / C body with Layered silicon powder and heated to temperatures of approx. 1500 to approx. 1800 ° C in a vacuum. Depending on Intended use, it is not absolutely necessary the entire C / C body to implement in C / SiC, but in general at least the surface layer becomes too C / SiC implemented. Although silicon melt infiltration is the preferred Procedure is, the C / C body also with other usual ones Process involving training in composite technology common Matrices are post-compressed. In particular, the liquid siliconization process can also be performed with silicon alloys, among others Contain metals such as chrome, iron, cobalt, nickel, titanium and / or molybdenum can.

The method described can preferably for Manufacture of brake discs or clutch discs can be used. Here, the compressible mass and at least in a cylindrical shape a core filled. The thickness of the bottom and top layer (below or above the Core zone) after pressing, preferably at least 7 mm. These layers form the friction layers of the brake or clutch disc. Form the brake or clutch disc is preferably that of an annular disc, d. i. the space near the axis is completely empty over the entire thickness of the pane. The shape and arrangement of the at least one core is preferred such that the formed cavities from the periphery of the cylindrical shaped body to the inner edge of the shaped body range and thus an open passage between the inner and outer cylindrical Form the edge of the washer. This means that internally ventilated brake or clutch discs with radial ventilation ducts.

According to the method according to the invention, brake and clutch disks are accessible in which the volume fraction of the reinforcing fibers in the core zone and in the layers above and below (massive) from one another by no more than 30%, preferably no more than 20%, and particularly preferably deviates by no more than 15%. In particular, a maximum deviation of up to 10% can be achieved by a suitable combination of thickness and compressibility of the core. This combination can be determined for each choice of molding compound and core material, core shape and number and applied pressing pressure by means of a test series. The compressible cores can even ensure that the volume fraction of the reinforcing fibers in the core zone lies above that in the zones above and below, preferably between 5 and 30% above the volume fraction in the adjacent zones, particularly preferably up to 20 % above, and in particular up to 15% above. The method enables a continuous transition between the zones with different fiber content; no sudden change is found, for example on the photograph of a cut or cut would manifest through a line or stripe.

The inventive method is based on the Illustrations closer explained. Show it:

1 2 shows a perspective view of a brake disc produced by the method according to the invention, the cover layer having been removed for the sake of clarity,

2 a perspective view of the same brake disc from a different angle,

3 a photograph of a green body cut away from the axis of rotation before carbonization, and

4 a photograph of a brake disc cut away from the axis of rotation after infiltration with silicon.

The oblique view of the 1 shows a brake disc 1 , in which the cover layer was removed, and in which the voids formed 2 are visible. In the area of the bridges 3 the material of the brake disc is formed from the mass introduced between the cores in the core zone. In the area of the periphery 4 the pressable mass, as explained above, does not have to flow around the cores of the brake disc. The 2 shows the same pane from a different angle, here the recesses partially show the inner area of the lower cover layer.

In the 3 a section through the pressed and hardened green body after the fourth method step is shown; the compressed cores 7 are from footbridges 5 surrounded by the molding compound. The same gray coloring of the material of a lower cover layer 6 like the material in the core zone 5 ' indicates that their density is the same.

In the 4 a section through the finished siliconized brake disc after the sixth process step is shown; here too the density is in the area of an upper siliconized cover layer 6 ' above the core zone 5 ' equal to that in the core zone 5 ' , The cavities formed at the site of the cores after pyrolyzing 7 ' correspond to the cores in their shape and size.

The according to the inventive method manufactured internally ventilated Brake or clutch discs can be used for automobile and truck brakes, for airplanes and rail vehicles as well as for Use friction clutches in all types of drives. So made hollow body are also versatile as components in tool and mechanical engineering usable.

1

brake disc

2

cavity

3

Stege

4

periphery

5

Stege

5 '

core zone

6

lower topcoat

H'

upper siliconized top layer

7

core

7 '

cavity

Claims (11)

Process for the production of hollow bodies from fiber-reinforced ceramic Materials, whereby - in the first step compressible cores are made, their shape at least in the plane perpendicular to the pressing direction essentially the Geometry of the cavities to be formed corresponds, - in the second step made a green body is in one form the compressible cores and a pressable and thermally curable Binder and pulp containing mass are filled, - in the third Step the pulp-containing mass is pressed, the cores in pressing direction are compressed by at least 5% of their extent in the pressing direction, - in the fourth The fiber-containing mass is cured, - in the fifth step the solidified green body by heating in a non-oxidizing atmosphere to a temperature of 750 ° C to 1100 ° C to a C / C body is carbonized, wherein the cores are made of material that in the fifth Step at least partially with volume shrinkage of at least 50% is pyrolyzed. A method according to claim 1, characterized in that subsequently to the fifth step - in the sixth step of the C / C body is infiltrated with a liquid metal while maintaining its shape at least partially a reaction of the carbon portion of the matrix of the C / C body with the metal to form carbides. A method according to claim 1, characterized in that - in the fourth Step the fibrous mass by heating to a temperature of 120 ° C to 280 ° C is cured A method according to claim 1, characterized in that the third and fourth steps overlapping simultaneously or partially in time accomplished become. A method according to claim 1, characterized shows that multi-layer cores made of foamed polymers are used in sandwich-like structures, at least one of the surfaces of the cores being covered by a hard polymer which is infusible under curing conditions. A method according to claim 1, characterized in that the pressable masses Contain carbon fibers with an average length of at most 50 mm. A method according to claim 1, characterized in that the pressable masses bunch made of carbon fibers with an average length below 5 mm. A method according to claim 2, characterized in that for Infiltration silicon or a silicon alloy is used. A method according to claim 8, characterized in that the Silicon alloy a metal selected from chrome, iron, nickel, Cobalt, titanium and molybdenum contains. hollow body made of fiber reinforced ceramic material available according to the method of claim 1 in the form of an annular disc the at least one cavity from the periphery to the inner edge the washer is enough. Use of hollow bodies according to claim 10 as Brake or clutch disc.